Solar cells which are generally used outdoors are used as a module sealed in some kind of a container or resin so as to avoid influences of moisture or dust, or to endure a collision of hail, a pebble, or the like or wind pressure. For example, a solar cell module which is called “superstrate structure” adopts a structure in which solar cells and an encapsulant are encapsulated between a glass plate and a back sheet. The encapsulant integrates members constituting the module with each other and shuts the solar cells off from influences of the outdoors, and it is concerned with durability of the solar cell module. As the encapsulant, those made of an ethylene vinyl acetate resin are widely used.
The solar cell module is manufactured by thermally bonding the foregoing respective members in a vacuum by a laminator. A work of this thermal bonding is performed by interposing a laminate obtained by laminating the module constituent members within the laminator between a diaphragm sheet and a hot plate, rendering a prescribed space within the laminator in a vacuum state, and heating the hot plate, thereby thermally dissolving and thermally crosslinking the encapsulant.
It is important that the thermal crosslinking of the encapsulant is achieved sufficiently and uniformly. This is because if a portion where the thermal crosslinking is insufficient is present in the encapsulant, separation of the module members from each other, invasion of moisture, and corrosion of the solar cells occur from the subject portion.
From the viewpoint of heat resistance, a silicone rubber has hitherto been widely used for the diaphragm sheet (Patent Document 1). But, the diaphragm sheet made of a silicone rubber involved such a problem that various performances are lowered due to repeated use, so that its durability is not sufficient.
Specifically, in the case of repeatedly using the diaphragm sheet, there were involved such problems that wrinkles are generated in the diaphragm sheet, thereby making it impossible to achieve uniform pressing during the lamination processing; and that the diaphragm sheet is abruptly broken during the lamination processing, thereby causing a production loss due to a replacement work of the diaphragm sheet and a lowering of the manufacturing yield.